Two-stage carburetion system



'July 9, 1957 H. A. CARLSON ETAL ,7 8,703

.TWO-STAGE 'CARBURETION SYSTEM 3 Sheeis-Sheet 1 Filed June 1, 1954 li nn .EICKMANN BY ATTORNEY July 9, 1957 H. A. CARLSON ETAL ,798,703

\TWO-STAGE CARBURETION SYSTEM 3 Sheets-Sheet. 2

Filed June 1, 1954 J y 1957 H. A. CARLSON ETAL 2,798,703

I TWO-STAGE CARBURETION SYSTEM Filed June 1, 1954 3 Sheets-Sheet 3 v INVENTOR. 'HARCLD A. CARLSON OLIN J. EICKMANN ATTORNEX United States Patent 2,798,703 TWO-STAGE CARBURETION SYSTEM Harold A. Carlson, Brentwood, and Olin J. Eickrnann, Normandy, M0,, assignors, by mesne assignments, to ACE Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application June 1, 1954, Serial No. 433,674 r 10 Claims. (Cl. 261-23) This invention relates to multi-stage carburetion sys- 15 terns for internal combustion engines and, more specifically, to a system for control of suction motor operated secondary-stage throttles in response to engine requirements.

Carburetors of the plain tubeengine aspirated type depend upon air velocity through a restriction of some type, usually a venturi, to produce the. necessary depression adjacent the end of an open fuel nozzle to cause the fuel to flow from the nozzle. Air velocity, at this point, depends upon pressure difference on opposite ends of the restriction which, considering atmospheric pressure at one end to be constant, is dependent directly on the suction applied at the opposite end. The amount of suction is a function of engine speed and throttle opening. So far as the carburetor itself is concerned, it is generally conceded that a small restriction will produce better atomization of fuel with a resulting better mixture distribution, but such a carburetor would be inherently of low capacity.

Engine requirements at low speed and low power out- 35 puts would probably be adequately served by acarburotor of low capacity such as above described, but, for maximum power and torque at any engine speed, the less the restriction in the induction system, the better. Full advantage cannot be taken of the efliciency inherent in modern high-speed, high-compression engines unless the carburetor permits free breathing.

This conflict between what is desirable in the carburetor by way of restriction and What is desirable to enhance overall engine efficiency, has brought about the introduction of multi-stage carburetion as a compromise. This system of carburetion provides the necessary restriction for proper operation of the carburetor and, at

the same time, added capacity to accommodate the re quirements of the engine.

In a multi-stage carburetor, it is usual to provide mechanism to perform the throttle opening in the primary and secondary barrels in a sequential manner, and only after certain air velocities have been reached in the primary. In order to accomplish this, it has been proposed to utilize the pressure drop in the primary venturi as a means of determining the proper conditions for opening of the secondary throttles. For instance, this has been proposed in the patent to Kishline, et al., No. 2,193,533. In the patented system, the secondary throttle valve of a two-stage carburetor is held closed by a calibrated spring and opened by a suction motor having a fluid connection with the primary induction conduit anterior to the throttle. Proper multi-stage operation requires the secondary to start to open as the velocities in the primary approach maximum, and to be fully opened by the relatively small increase in velocities as maximum is reached. A spring which will react properly in response to the effect of small variations in the pressure available 7 to operate the suction. motor must be one which exerts substantially a constant resistance independent of change 2,798,703 C Patented July 9, 1957 2 in length. The spring would have to be sensitive and necessarily difficult to calibrate and hold in adjustment.

The present invention is aimed at providing an improvement in the basic system disclosed by Kishline,

which results in a radical change in the mode of operation. In the present invention, the initiation of the operation of the secondary throttles and their amount of opening is determined by a function of primary throttle opening and engine speed. The rate and amount of opening of the secondary throttles is independently modified by a valve operated in response to secondary throttle movement.

A modification of this invention provides the same result as above stated, but requires a minimum open position of the primary throttles before operation of the secondary.

In the drawings:

Fig. 1 illustrates a four-barrel, multi-stage carburetor with parts in section to illustrate the present invention.

Fig. 2 is a fragmentary side elevation partly in section illustrating a first modification.

Fig. 3 shows a second modification which can be applied to either Fig. 1, Fig. 2 or Fig. 4.

Fig, 4 is a fragmentary side elevation partly in section illustrating a third modification of the invention.

The carburetor illustrated is of the type shown in the patent to Bicknell No. 2,640,472 of June 2, 1953, and has two pairs of down-draft induction conduits arranged in a unitary structure. One of each pair is shown in the drawings. The primary induction conduit contains a pair of venturi 11 and 12 arranged in superposed concentric relation within the induction conduit and disposed in a manner so that the aspirating effect of one is imposed upon the other. The secondary induction conduit 14 has similarly arranged venturi 15 and 16. Each of the induction conduits 10 and 14 mount pivoted throttle valves 17 and 18, respectively, for controlling the outlet from the mixture conduit.

In order to supply fuel to the mixture conduits, the carburetor is constructed with concentrically arranged fuel bowls 19 and 20, and fuel therefrom is supplied through metering orifices 21 and 22 in the bowl portions 19 and to inclined main fuel passages 23 and 24, which extend to fuel nozzles 25 and 26 in the venturi 11 and 15, respectively. Each of the fuel passages 23 and 24 communicates with idling wells 27 and 28 which are connected by idling tubes and the passages 29 and 30 with idling fuel nozzles 31 and 32 in the mixture conduits 10 and 14, respectively. These fuel nozzles open adjacent the edges of throttles 17 and 18. The fuel nozzle 31 has a suction bleed controlled by an adjustable metering screw 33 for adjusting the mixture supplied through the primary mixture conduit 10 during the closed-throttle operation.

The entrance of air to the primary mixture conduits 10 is controlled by a choke valve 35 operated by an automatic choke control of any Well known type located Within the housing 36.

Rigidly secured to the primary throttle shaft 38 is a 0 radially projecting finger 39. This finger co-operates with an outwardly extending lug 40 on an arm 41 loosely mounted on the primary throttle shaft 38. Arm 41 is connectedby a link 42 with a bell crank 43 rigid with the projecting end of the secondary throttle shaft 44. The

5 other arm of the bell-crank 43 indicated as 45 is connected by a rod 47 to a diaphragm 48 clamped between suction motor housing parts 49 and 50. Housing part 49 may be integrally formed with the body portion of the carburetor by cast ribs 51and 52.

One side of the diaphragm 48 is exposed to atmospheric pressure which may enter the suction motor housing through the opening 55 surrounding the rod 47. The

opposite side of diaphragm 48 is exposed to pressures communicated thereto by way of a passage 56 in the part 5 2 of the housing which is in alignment with a passage 57 extending downwardly to the body of the carburetor within the rib 52.

Within the body of the carburetor is a passage 59 communicating with the passage 57 and extending to a port or ports 60 in the venturi 12 within one or both of the primary mixture conduits 10. The passage 59 has a branch 61 extending into the journal bearing for the secondary throttle shaft 44. A valve portion 62 on shaft 44 controls the entrance of air through the bleed opening 65 to the branch passageway 61. Spring 64 holds the secondary throttles closed.

Secured to the opposite end of the throttle shaft 38 is an arm 70 having a hole 71 for connection with the accelerator pedal of the motor vehicle.

Operation of the accelerator pedal of the motor vehicle controls the position of the lever 70, the throttle shaft 38, and the primary throttles 17, one of which is shown. A suitable spring may be connected with the arm 70 to return the primary throttles to closed position. Closing movement of the primary throttles engages the lug 39 with the lug 4t! and closes the secondary throttles through the connection of link 42 with the bellcrank 43.

With the engine operating, primary throttle opening will increase engine speed at a rate depending upon engine load. During the early stages of engine acceleration, the secondary throttle will remain tightly closed by the force exerted by spring 64 on the rod 47. When the velocity through the venturi 12, which depends on engine speed and throttle opening, reaches a predetermined amount, suction at the ports 60 will cause a sufficient depression with the passages 56, 57 and 59 to overcome the spring 64. This action will be delayed by the modulating effect produced by the atmospheric bleed 65. As spring 64 is compressed, the secondary throttles open and valve 62 will begin to close the atmospheric bleed 65, which will increase the suction within the chamber within casing 50 of the suction motor and increase the force applied by the suction motor. With valve 62 completely closed, full suction at the ports 60 will be communicated to the chamber within casing 50 to exert the maximum opening effect upon the secondary throttles to cause an increase in the rate and/or amount of opening of the secondary throttles until the lug 40 contacts the lug 3?. Full opening of the primary throttle will cause the secondary throttles to follow, providing engine speed increases, until both sets of throttles 17 and 18 are wide open. Only a slight. increase in engine speed i may be necessary to open the secondary throttles fully. It" the load on the engine increases to decrease engine speed to the point where the suction at the port 60 is not suificient to hold the secondary throttles open, spring 64 will. urge the secondary throttles toward closed position even. if the primary throttles remain wide open. The degree of closing will be strictly a function of engine speed, which, alone, determines velocity in the primary mixture conduits under these conditions. If secondary throttles close sufliciently to again open the valve 62, the modulation of the atmospheric bleed will permit the secondary throttles to be closed by the spring 64.

Turning now to Fig. 2, the drawings show a mechanism which is the full equivalent of that shown in Fig. 1 and described above. Similar parts have been given the same reference characters, and the description here will emphasize the differences in construction. The primary mixture conduits are provided with throttles 17, which are manually operated by a lever (not shown) directly connected to the accelerator pedal in the vehicle. Shaft 38, mounting the primary throttles, carries a lug 39 which co-operates with a lug 40 on a lever 41. A link 42 connects lever 41 with one arm 43 of a bellcrank rigidly attached to the secondary throttle shaft 44 mounting secondary throttles 18. The opposite end 45 of the bellcrank 43 connects with the rod 47 attached to a diaphragm ,4 48. The diaphragm, in turn, is clamped between housing parts 49 and 50 of a suction motor. Spring 64 interposed between the housing 50 and the diaphragm 48 constantly urges the secondary throttles 18 into closed position. The suction motor is integrally formed with the body of the carburetor by supporting ribs 51 and 52. A passage 55 provides clearance for operation of the rod 47 and admits atmospheric pressure to one side of the diaphragm 48.

Suction from the primary mixture conduits 10 is communicated to the chamber within the suction motor housing part 50 above the diaphragm 48 by a series of passages 56, 57 and 59 communicating with the ports 60 in the walls of the venturi 12.

This structure is substantially identical, so far, with that above described. However, the function of the bleed passage and the valve 62 is performed by an entirely different mechanism than that shown in Fig. 1.

In Fig. 2 the function of the valve 62 is performed by a metering rodforming a continuation of the rod 47, which metering rod 80 is received in an orifice 81 formed centrally of the upper housing part 50. This metering orifice 81 may communicate directly with atmosphere as is shown in this modification, or be connected with atmosphere by a tube leading to any convenient source of pressure within the upper part of the mixture conduits 14 above the venturi.

The operation of the structure shown in Fig. 2 will be exactly the same as that described for Fig. 1. As the secondary throttles open in this modification, the atmospheric bleed 81 communicating with the chamber within the housing 50 Will be progressively throttled by the metering rod 80. In this modification, initiation of the operation of the secondary throttles and their amount of opening will be determined as a function of primary throttle opening, which is manually controlled, and engine speed, while the rate and amount of opening of the secondary throttles is independently modified by the progressive throttling of the metering rod 80 in the atmospheric bleed 81.

Turning now to Fig. 3, a second modification of the invention shown in Fig. l is illustrated, and similar reference characters have been used to indicate like parts. This description will be confined to pointing out the difference in structure over that shown in prior disclosed devices.

In the modification shown in Fig. 3, primary throttle shaft 38, which mounts the primary throttles 17, is provided with a valve 85. Bleed passage 59 leads directly to the journaled bearing supporting the throttle shaft 38 and containing the valve 85. The ports 60 within the primary venturi 12 also connect by way of passage with the journal bearing supporting the primary throttle shaft 38, so that communication between the ports 60 and the passage 59 is controlled by the valve 85. This valve is so arranged that suction will not be communicated from the ports 6% to the suction motor housing 50 until the primary. throttles have moved a substantial amount from closed position, preferably 60 or 70 degrees. For this reason, no secondary throttle opening will be permitted within the range of movement of the primary throttle from closed to 60 or 70 degrees open.

By thismodification applied to the construction of Fig. 1, the secondary throttles will hold closed until the primary throttles have reached a certain amount of opening. Once the primary throttles have reached this degree of opening, however, then the amount of opening of the secondary throttles will be determined as a function of engine speed while the rate and amount of opening of the secondary throttles will be independently modified by the valve 62 which controls the atmospheric bleed 65, all as above explained in the description of Fig. l.

The modification in Fig. 3 can also be added to Fig. 2 and will operate as described above.

Turning now to Fig. 4, a third modification of the invention shown in Fig. 1 is illustrated, and similar reference characters have been used to indicate like parts. This description will be confined to pointing out the differences in structure from that shown in prior modifications.

In the modification shown in Fig. 4, primary throttle shaft 38, which mounts the primary throttle 17, carries a lug 39 which co-operates with lug 40 on lever 41. Closing action of the throttle 17 will engage lugs 39 and 40 to close secondary throttles 18 through the connection 42 with the bellcrank 43.

Secondary throttles 1 8 on throttle shaft 44 are actuated through a rod 47 connected to the diaphragm 43 of a suction motor. A spring 64 tends to maintain throttles 18 closed.

Ports 60 within the primary mixture conduit connect by way of the passages 59, 57 and 56 with the chamber of the suction motor. This connection is controlled by a stepped metering pin 95 fixed to the rod 47 and operating within the opening in a metered orifice 96 controlling the passage 56. Located in the secondary mixture conduits adjacent the edge of the throttles 18 are ports 98 which connect with passage 99 leading to metering orifice 100 in the wall of the chamber of the suction motor.

Operation of the modification in Fig. 4 is similar to that shown in Fig. 1 as above described. In this modification, however, movement of the secondary throttles controls the suction bleed passage 56 by the metering pin 95. The effect of the suction passage is modulated by the fiow of air through the ports 98 when the secondary throttles are closed. At a certain degree of primary throttle ope ing and engine speed, suction at the ports 60 will produce sufficient depression within the chamber of the suction motor to crack the throttles 1 8. When this happens, the ports 98 become subjected to depression due to the velocity of the gases passing around the edges of the throttles 18, which will cut down the effectiveness of the ports 98 as an atmospheric bleed :and apply more power through the suction motor to open the secondary throttles. This will drop manifold suction and tend to reduce the effectiveness of ports 60 but as the motor moves the throttles 18, the restriction in the orifice 96 will become less, so as to continue opening movement of the secondary throttles 18. Generally speaking, however, the effect of the metering pin 95 will control the amount of secondary throttle opening while the rate of throttle opening is aflected by the action of the secondary throttle on the bleeds 98.

The net result in all of these modifications will be that the action of the primary and secondary throttles is sequential during their opening movement-that is, the primary opens first, and then the secondary. During the closing movement, however, the action is usually reversed, with the secondary closing ahead of the primary.

A structure has been described and illustrated which will fulfill the objects of the invention, but it is contemplated that other modifications will be apparent to those skilled in the art which will come within the scope of the appended claims.

We claim:

1. A two-stage carburetor system comprising primary and secondary induction conduits, primary and secondary throttle valves, respectively, therein, manual means to actuate said primary throttle valve, yielding means urging said secondary throttle valve closed, a suction motor operatively connected to said secondary throttle valve for opening the same against said yielding means, a suction connection between said motor and a portion of said primary conduit, a bleed duct connecting said motor to a zone at substantially higher pressure than said portion of said primary conduit during first-stage operation of said system, and means to reduce the effectiveness of said duct as a bleed during second-stage operation of the system comprising a valve in said duct and an operative connection between said last-mentioned valve and said secondary throttle valve.

2. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttle valves in said conduits, a positive acting connection fior operating said primary throttle, a motor operatively connected to said secondary throttle having a con nection with a source of engine power controlled by said primary throttle, and valve means operated by said motor and associated with said connection with the source of engine power for modifying secondary throttle opening by said motor.

3. A two stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttle valves in said conduits, a positive acting connection for operating said primary throttle, a motor for operating said secondary throttle having a connection with a source of engine power controlled by said primary throttle, and means operated by said secondary throttle .and associated with said connection with the source of engine power for modifying secondary throttle opening by said motor.

4. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttle valves in said conduits, a positive acting connection tor operating said primary throttle, a motor op eratively connected to said secondary throttle having a connection with a source of engine power controlled by said primary throttle, valve means operated in response to movement of said secondary throttle by said motor and associated with said connection with the source of engine power for moditying the amount and rate of secondary throttle opening by said motor, and means tor positively closing said secondary throttle by closing action of said primary throttle.

5. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttles in said mixture conduits, a positive acting connection for operating said primary throttle, a spring for closing said secondary throttle, a motor for opening said secondary throttle against the variable increasing resistance of said spring, a connection from said motor to a variable source of engine power controlled by said primary throttle, and means associated with said secondary throttle for compensating at least in part for the increase in resistance of said spring as said secondary throttle opens.

6. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttles in said conduits, respectively, a positive connection for operating said primary throttle, a suction motor operatively connected to said secondary throttle, a suction connection between said motor and said primary mixture conduit whereby said motor is actuated and said secondary valve opened upon increases in. suction in said primary mixture conduit, and valve means operated by said motor and associated with said suction connection and said secondary throttle to modulate the effective suction applied to said motor in accordance with the position of said secondary throttle.

7. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttles in said conduits, respectively, a positive connection for operating said primary throttle, a suction motor operatively connected to said secondary throttle, a suction connection between said motor and said primary mixture conduit whereby said motor is actuated and said secondary valve opened upon increases in. suction in said primary mixture conduit, and means associated with said suction connection and said secondary throttle to modulate the efiective suction applied to said motor in accordance with the position of said secondary throttle, said means including an atmospheric bleed and valve means actuated by said secondary throttle.

8. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttles in said conduits, respectively, a positive connection for operating said primary throttle, a suction motor operatively connected to said secondary throttle, a suction connection between said motor and said primary mixture conduit whereby said motor is actuated and said secondary valve opened upon increases in suction in said primary mixture conduit, and means associated With said suction connection and said secondary throttle to modulate the ei ective suction applied to said motor in accordance With the position of said secondary throttle, said means including an atmospheric bleed and a metering rod in said bleed operated by said suction motor.

9. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttles in said conduits, respectively, a positive connection for operating said primary throttle, a-suction motor operatively connected to said secondary throttle, a suction connection between said motor and said primary mixture conduit whereby said motor is actuated and said secondary valve opened upon increases in suction in said primary mixture conduit, a valve in said suction connection operated by said primary throttle, and means to modulate the effective suction applied to said motor in accordance with the position of said secondary throttle,

10. A two-stage carburetor system comprising primary and secondary mixture conduits, primary and secondary throttle valves in said conduits, a positive acting connection for operating said primary throttle, a motor for operating said secondary throttle having a connection with a source of engine power controlled by said primary throttle, and means operated by said throttles and associated with said connection with the source of engine power for modifying the rate and amount of response of said motor.

References Cited in the file of this patent UNITED STATES PATENTS 2,313,258 Olson Mar. 9, 1943 2,376,732 Strebinger May 22, 1945 2,390,019 Winkler et al. Nov. 27, 1945 

